Process for bleaching and the like purposes



PROCESS FOR BLEACHING AND THE LIKE PURPOSES Filed 001:. 16, 1925 2Sheets-Sheet 1 Iwlef pass 16:

0112222 passage supply ZanKS 5 LL 2 26621 756 6077c em raior" 2a iqzaazz'zer' fewer" CiZzzZe 27 11" dza-mber Nozzle Tower C72 wi 3| FlqlPatented Sept. 27, 1927.

UNITED" STATES PATENT OFFICE.

CARL BUBCE THOBNE, H AWKESBUBY, ONTARIO,,CA'HADA.

' PROCESS IORIBLBAOHING AND THE LIKE PURPOSES.

Application am October 18, 162 sum in. 68,873.

and the objects of the invention are to insure.

a regular and uniform supply of pulp to the bleaching apparatus, to reuce the period of time required for bleaching; to produce a pulp ofbetter uality by the use of a new method of bleac ing partly. athlghdensl'ty and partly at low density; to eliminate mechanicalagitation of the pulp as much as possible; to produce a pulp of hlgherphysical strength, of greater purlty chemlcally, of better color andsuperior in its cellulose properties; and generally to provide anefiicient, economical and faster bleaching method, and it consistsessentially of the various steps performed in or about the order setforth in detail-hereinafter and set forth in the claims which follow theexplanation of the invention.

In the drawings, Figure 1 is a dlagrammatic view showing the system offeeding the high density pulp bleaching agent and water ina continuousand uniform manner to the bleaching tower.

Figure 2 is a dia ammatic' view showing one arrangement or bleachingpartly at hi h densityand partly at low denslty.

igure 3 is a dia rammatic view showing the new system of feeding combned with a system for bleaching partly at hlgh density and partly at lowdensity.

Like numeralsof reference indicate corres onding parts in the Variousfigures.

n this method of bleaching it is not essential to' include allthe partsillustrated, as under certain conditions all of the bleaching may bedoneat high density, instead of being 40 done partly at high density andpartly at low density, and under other conditions the systemof .feedingmay be simplified, for much .-'depends on the requirements of the tradeand also "upon the local conditions where the process' is being used.This and the accom- 'aiiying application Serial No. 61,075, filedfctober 7, 1926 are made to clarify copend- 1 ing-applicationfiled'under Serial Numbers 387 and 755,691, on December 6, 1924,

Q; December 13, 1924, respectively and are {intimately associatedtherewith.

- The supply of pul flows from the mill through the passage 10 to aconcentrator 11 where suflicient water is taken from the pulp to bringit up to the desired density. From the concentrator the pulp flowsthrough the outlet passage 12 to the equalizer tower 13, the bottom ofwhich tower is of the hopper type, and inclined to a central outlet 15around which the scraper arm 16 continually travels. The arm 16 isfixedly mounted on a shaft 17 extending centrally and vertically throughthe tower 13 and is suitably driven at a uniform speed. The arm 16rotating at a uniform speed kee s a continuous stream of high densitypulp, owing to the opening 15 along the chute'18 to themixer 19. Thecapacity of the equalizing tower 13 is such that it will produce a veryuniform andeven flow at its ofpening .15 irrespective of whether theflow o pulp preceding the equalizing tower is uniform or not.

The chute 18 leads the ulp from the outlet 15 continuously towar s themixer outlet 25. During its passage through the mixer, waterandbleaching agent are addedthrou h the pipes 20 and 21 respectively, fromt 0 supply tanks 22" and 23, which tanks are fitted with the requiredflow boxes, so that exact quantities of water and bleaching agent can becontinuously added.

The pulp, bleaching a ent and water are mixed by the rotating pa dles 24and the resultant mixture discharges through the o ning 25 along thechute 26 to the bleac ing tower 27 through the inlet 28 at the upperend. This bleaching tower has three arms mounted on the central shaft17, one a levelling arm 29, near the top of the tower for the purpose oflevelling and spreading the mass out evenly as it enters the tower,another situated below the middle of this tower, this is a perforatedarm 30, forming an air nozzle communicating with the interior of theshaft 17 which is hollow in this tower, this shaft in turn beingconnected to a compressed air supply. The third arm in this tower is ascraper arm at the bottom similar to the one in the equalizing tower,described above.

The tower 27 is of similar shape to the tower 13' and has the hopperbottom 31 and central outlet 32, and the scraper arm 33 maintains acontinuous even flow of pulp mixture into the chute 34 leading to thewasher 35, where the bleaching agent is washed out of the pulp and if itis desired toend the bleaching here, then the pulp proceeds to athickener and from thence to a stock chest.

The method thus described points out a quick process of bleaching athigh density, whereby the feed is regulated and automatically equalized,but it is not always desirable to complete the bleaching at highdensity, and in Figure 2 it is shown that following the high densitybleaching performed in the tower 42 of the pulp received from the mixer43, the resulting product is washed in the receptacle 35 and emptiedinto a suitable mixer 40 for a fresh mixing of the bleaching agent and.water and then passed on toa low density vat 41, many forms of which maybe used, therefore it is not necessary to maintain an equal densitythroughout or keep to the hi h density, as for some manufactures lowensity bleaching can readily be introduced in conjunction with the highdensity when and where wanted. The process of bleaching in two stages,that is by partl bleaching at a high density and then comp eting thebleaching at a low density has proved to be most beneficial to thefinal-product and as a method of bleaching has never been known before,so far as I am aware. Also the mixing of the pulp and bleaching agent ina separate apparatus prior to the bleaching at high density is alsonovel, thou h in my copending application Serial Number 754,387, filedDecember 6th, 1924, it is described in connection with a high densitybleaching system which also mentions bleaching by stages but each timeat a high density.

There are, of course, a number of high density bleaching systems, any ofwhich ma be used in connection with this rocess an also a great numberof low ensity systems, and. naturally it is entirely a matter of choiceas to the most desirable system, though so far as the high densitysystem is concerned, it is preferable to use the particular processdescribed herein and already mentioned in the earlier applicationv inorder to obtain the best results.

In the high density bleaching1 system described above, the pulp is bleacd at a density of from 15 to 20% or more, while in the low densitysystem the density may be from 10 to 5% oreven lower. The final productproduced by the above system of bleaching is a pulp of higher ph sicalstrength, of greater purity chemical 1y, of better color, and superiorin its cel ulose properties, also this better quality product isproduced with considerable saving of cost in time, power and bleachingagent.

It is to be understood that while this process is intended mostly forthe purpose of bleaching pulp for paper making, artificial silk andother manufactures, it may be used in many other arts, with advantageand economy, and the fact that while one use only is described herein,it will in no way confine the invention to any particular purpose orindustry.

What I claim is 1. In a process of the character described, cons stingin concentrating the pulp for feeding purposes, then directing the feedinto an enclosed passage and discharging it at the same rate, andthereby maintaining a column afiording constantly even pressure, thenmixing the discharged pulp in passage with bleaching agent and water anddis" charging it to'the bleaching area and continuously delivering thebleached pulp at the same rate as the original feed.

2. In a process of the character described, consistmg in feeding thepulp at a regulated rate and pressure, then mixing the bleaching agentand water with the passing pulp and fixing the density, then partiallybleaching the prepared pulp, then again mixing the partlally bleachedpulp with bleaching agent and water and fixing a density varying fromthe aforesaid density and finally bleaching at the latter density.

3. In a process of the character described, conslsting in maintaining aneven pressure at the feed discharge to the mixer, then fix ng thedensity for bleaching and introducing the bleaching agent, then slowlypassing the pulp through the bleaching areaand comcidently expelling thedecomposition gases by air under pressure, then mixing with bleachingagent and water and reducing the density and finally bleaching underordinary low density conditions.

4. In a process of the character described consisting in building uptwo. columns of pulp continuously discharging at the lower end and fedby falling pulp .at the upper end to compensate for the discharge,introducing the mixing ingredients for the bleaching between saidcolumns and be 0nd the discharge of the lower column, was ing andthickening prior to the second mixing and finally bleaching at lowdensity.

5. In a process of the character described, the accumulation of pulp ina succeeding vessels partially fille the maintenance of a steady fallingof the several accumulations, the passing of the pulp in an indirectpassage from vessel to vessel and mixing t e bleaching agent with thepulp entering the second vessel, the feeding of air in the secondaccumulation in a direction contrary to the fall and mechanically distributing said air and passing the pulp on and finally finishing.

6. 1n a process of the character described, consisting in concehtratingthe pulp at a high density and delivering in a falling mass,accumulating the falling mass below the fall and forming a non-turbulentmass constantly discharging at the rate of the fall, agitating thedischarge and directing it (plurality of lni) under a regulated feed ofbleaching agent and water, passing this on to a second nonturbulent massconstantly added to and discharging, and feeding compressed a1r throughthe bleaching mass in a direction contrary to its fall.

7. The herein described process of bleach ing pulp, consisting infeeding the pulp to the bleaching zone, mixing the pulp with thebleaching agent and water and bleaching, repeatin the aforesaid stepsand varying the density of the pulp relatively in respect to saidrepetitions.

8. The herein described process of bleaching pulp, consisting in feedingthe pulp, regularly to the bleaching zone, mixing the pulp with thebleaching agent and water, bleaching at a density of pulp of tosubsequently mixing again with the bleaching agent and water andbleaching at a density of, pulp of-10% to 5%.

9. The herein described process of bleach-' ing pulp, consisting inpouring out a stream of dense pulp and forming a column thereof, mixin ableaching agent and water with the pulp alling from said column,discharging the pulp mixture to the bleaching zone and. forming anothercolumn, in which the bleaching occurs, and aerating during theoperation'of the bleaching agent.

10. The herein described process of bleaching pulp, consisting inconcentrating the pulp, continuously discharging and forming a stream-offalling pulp, introducing a bleaching agent and water intermediately ofthe height of the stream without interrupting its'flow, bleaching thepulp in passage following the mixing of the bleaching agent anddischargin the continuously flowing stream and was ing.

11. The herein described process of bleaching pulp consisting inconcentrating the pulp, discharging the pulp in a falling mass,accumulating the falling pulp, regulating the fall below theaccumulation, agitating the pulp falling from said accumulation andcoincidently mixing therewith a bleaching agent and water, continuouslydischarging the mixture, then bleaching the falling pulp anddistributing air therein and maintaining the mixture in a non-turbulentcondition during the bleaching and aerating and then washing.

Signed at Montreal, Can. this 26th day of September, 1925.

CARL BUSCH THORNE.

